From Cavities to Channels in Host:Guest Complexes of Bridged Trianglamine and Aliphatic Alcohols

Abstract

We demonstrate that covalently bonded chiral organic hexaamine, rigidified by a methylene bridge, assembles into crystalline inclusion compounds and microporous materials. The inclusion of primary alcohol molecules belonging to the homologous series from ethanol to n-octanol is intrinsic to the triangular molecular shape and columnar stacking of these triangular units. Our studies show that through the choice of differently sized guest molecules (short- or long-chain) we were able to increase the accessible solvent volume from cavities, located inside columnar stacking of triangular units, to one-dimensional undulating channels. While the short-chain molecules occupy voids, the long-chain molecules are included in the channels. By using branched chain solvent during crystallization we were able to isolate dimorphic apohost forms that give rise to two different types of new materials: porous crystals with 1D channels and crystals that possess isolated 0D pockets.